Re: Routing loops & TTL tracking with tunnel devices

[Jason A. Donenfeld]

Hi Eric,

On Sat, Apr 30, 2022 at 12:05 AM Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
> I assume you add encap headers to the skb ?

Yes; it's encapsulated in UDP, and under that some short header.
However, everything under that is encrypted. So,

> You could check if the wireguard header is there already, or if the
> amount of headers is crazy.

so it's not quite possible to peer down further to see.

> You also can take a look at CONFIG_SKB_EXTENSIONS infrastructure.

Blech, this involves some kind of per-packet allocation, right? I was
hoping there might be some 6 or 7 or 8 bit field in sk_buff that's not
used anywhere on the TX path that maybe I could overload for this
purpose...

Jason